Something I don't understand about the "click-no-start" and the TRS...
When I put the transmission lever in anything but P or N, I don't get even a click. So for those who get just a click, why does moving the lever usually allow it to click and start?
It's unclear whether people are hearing the click from the starter relay in the TIPM, or the solenoid on the starter. If the electricity gets to the point where either one clicks, it should indicate all is well with the TRS.
It's tough to say it is the TRS. If you hear the starter solenoid click it is usually an indication the circuit from the key to the starter is functional...but not always. The TRS uses very small contacts to complete the starter circuit, they run in trans fluid which is often dirty or contaminated.
Electrical circuits fail when they are under a load, that is why we perform voltage drops on the circuit while the load is present. I can't tell you how many times I have had mechanics tell me they checked continuity on a circuit and it was good. They use an ohm meter and see continuity under 100 ohms and stop. They are surprised to see the circuit fail when plugged in and under a load.
It is possible, and common, for there to be enough continuity for the TRS to complete the starter circuit momentarily, then when under a load it goes open, or fails. If the starter solenoid is clicking hard and no crank it may be a starter but that would negate the jockeying the shift lever.
Jockeying the shifter around may establish better contact resulting is a successful start. There is also a host of other circuits involved depending on options, like the TIPM, WCM, etc. There are also software updates and ground issues, it goes on and on. Hands on it can be an easy diagnostic, but can be confusing for the average guy.
There is no guarantee this is the case but it is one likely cause. Grounding pin #10(yel/blu) at the green TRS connector will bypass the neutral safety function and eliminate the TRS. I find guys are reluctant to test the TRS circuit since it is a little difficult to get too, and a pain to replace the TRS. Another good reason for our circuit, no need to take the transmission apart.
I try and keep advice short and simple. I can write two pages on technical mumbo jumbo then they guy posts he had a loose battery cable or bad battery. I assume all that is checked prior to a diagnostic but you know what happens when you assume.